Metal, and particularly copper, cables are deployed in a variety of industries such as the telecommunications, rail, and power sectors as a conductive medium for the transmission of e.g. telecommunications signals and electricity. When essential transmission lines are damaged, the resulting consequences can be far-reaching with potential loss to life and limb and a threat to national security. The extent of damage to the cable itself ranges from the relatively minor (resulting in a reduction of the cable's transmission capacity) to major structural damage affecting the physical integrity of the cable. This includes breaks, splits, partial cuts, and at an extreme, a complete cable cut. Cables are inherently at risk on a day-to-day basis: for example, it is not unusual for cables to be accidentally cut through by an excavation vehicle, or damaged through deliberate vandalism. In recent times, this risk is worsened by soaring scrap metal prices, which has in turn escalated the number of metal theft incidences worldwide. In such cases, not only has the damage to be repaired, but the length of stolen cable has to be re-provisioned and -installed, requiring even more time and cost for the resumption of normal service.
In addition to the task of detecting cable damage in the first place, there is the issue of identifying the location of the damaged cable in often extensive copper networks, for which comprehensive and up-to-date asset records and registers may not exist. As might be expected, it is crucial to pinpoint the location of the damage without delay, particularly in the context of hoping to catch copper thieves in the act and before the cables are removed from the installation.
In specific applications in the telecommunications sector, copper cables are typically deployed mainly in the access network. Depending on the chosen network architecture, copper lengths are provided between the customer premises to the local exchange or to points closer to the customer e.g. to the street cabinet (FTTC), to the curb, or the like. Even in a theoretically all-fiber Fiber to the Premises/Home access network implementation (FTTP/FTTH), a legacy voice Plain Old Telephone Service (POTS) copper network might remain in use in parallel to the fiber network.
These lengths of copper are vulnerable to the kinds of damage discussed above, and are also potential targets for metal thieves. The metal theft epidemic is reaching crisis levels, with governments passing new laws in attempts to contain the problem. Security measures in use in the UK presently include use of physical locks, fencing and barbed wire, video camera and alarm systems, and marking copper plant with SmartWater™ (a liquid containing a chemical code for identification, which is invisible to the naked eye). British Telecommunications plc (BT plc) also have a dedicated Metal Theft Task Force, which is tasked to operate the security systems and to thwart and respond to such incidents by gathering and analyzing intelligence from cable theft incidents, as well as to help disrupt disposal routes for stolen metal. Yet other solutions proposed involve laying a spare cable alongside all existing cables for the purpose of detecting cuts, which are periodically line tested, which is seldom commercially feasible or practical. Cables with reduced copper content to make them less valuable to thieves have also been developed, but this approach does not address the difficulties faced in already-deployed cables.
An issue concerns the location of the problem within a geographically extensive network, which typically extends the length and breadth of a region or country. In most countries, the access network comprises copper cables in whole or in part, which will be the target for copper thieves. However, network faults adversely affecting service can arise anywhere i.e. outside the access network in the core network. While optical fiber is the more typical transmission medium in the core, it is not unknown for less experienced would-be copper thieves to dig up fiber cables located in the core network and elsewhere in error.
The cost to network operators and owners is, as might be excepted, immense. In the UK, the large volume of connection faults arising from damage caused e.g. by copper theft directly result in considerable network downtime as repair activity gets underway locating and identifying the location and cause of the fault (which may itself take hours, even before repair work begins). This results in significant time and cost to all parties, and network operators suffer harm from an often-unquantifiable but very real loss in customer goodwill.
A method of detecting problematic links in the core network is described in EP494513, in which telecommunications traffic over optical fibers in the core network is re-routed to avoid a faulty link identified by using line termination equipment to track and count line synchronization errors. This method cannot however be used for the speedy identification or localization of damage or cuts to metallic wire or cable especially in the access network.
It would be desirable to detect cable damage such as cuts in real time or near-real time in such a way so as to impart a high level of confidence in the system's findings, which at the same time also identifies the cable damage location within a network, in the form of a solution which is economically viable, deployable in practice within an existing network and requires little infrastructure change. The detection process should ideally be capable of identifying and locating faults within the access network, caused by events or incidents from outside the access network, and regardless of the underlying broadband or other technology being used within the network. There are now no known economically viable solutions to detect cable cuts or other damage and to swiftly identify the damage location(s), using existing network infrastructure or which involve very little change or adaptation of existing methods or systems so as to allow for immediate deployment and adoption.